Production of cross wound bobbins



Jan. 30, 1951 P. A. BEEFTINK 2,539,942

' PRODUCTION OF CROSS wounn BOBBINS Filed Dec. 18, 1947 I N VEN TOR.

A TTOENEY Patented Jan. 30, 195i UNITE- PRODUCTION OF CROSS WOUND BOBBINS Petrus Andries Beeftink, Breda, Netherlands, as-

signor to American Enka Corporation, Enka;

N. 0., a corporation of Delaware Application December 18, 1947, Serial No. 792,628 In the Netherlands March 24, 1947 Claims.

The present invention relates to the production of cross wound packages of yarn, and more particularly to winding normally twisted rayon (75 to 150 turns per meter) into package form utilizing a predetermined pitch which renders the package suitable for subsequent high twisting operations, such as, for example, imparting to the yarn more than 500 turns per meter.

In high twisting operations, it is customary to use supply packages that have been wound onto flanged bobbins. These flanged bobbins are mounted on a throwing spindle of an uptwister and are rotated at a speed that bears the proper relation to the speed of the takeup device in order to effect the required number of turns per meter. As set forth in the Ramsdell Patent No. 2,119,963, the use of these flanged bobbins incurs several disadvantages. The hollow core upon which the yarn is wound must have a rather large diameter, 1. e., about 60% of the diameter of the flange of the bobbin. Consequently, there is much lost space in the center of the bobbin, and in addition, the yarn body is located so far from the mathematical axis that the air resistance and themoment of inertia of the full bobbin is so high that the power consumption is greatly increased during rotation at high speeds. Another disadvantage of the thick core is that large quantities of yarn cannot be wound onto the flanged bobbin which necessitates interrupting the twisting operation more often. The flanges of the bobbin also present edges over which the yarn can rub, thereby subjecting the yarn to possible damage. Finally. the flanged bobbins oifer a large percentage of dead weight during transportation.

The above mentioned patent recognized these difiiculties and attempted to provide a cross wound package that would overcome these disadvantages. However, this patcnt was concerned with the production of packages weighing only up to A of a pound, and in fact preferred packages containing only 4 or 5 ounces of yarn. In order to produce such a package, a traverse ratio of 4:1 was used. The patentee made no mention of the length of the support on which the package was wound and consequently it should be assumed that the 4:1

ratio was maintained throughout the windingon period regardless of the length of the package being prepared. Consequently, whatever the advantages the patentee may have achieved must have resulted from the maintenance of a constant traverse ratio which would necessarily alter the pitch for different length packages. Whatever advantages were achieved by this invention apparently were not suflicient to permit rotation of the packages during the subsequent high twist operation at a speed above 11,000

R. P. M. Moreover, comparatively small packages e (not exceeding 350 gms.) were utilized.

As distinguished from the priorpractice, including the above mentioned patent, it is contemplated by the present invention to wind a large quantity of yarn, at least 350 gms. and preferably above 500 gms. onto light-weight cores made of a material such as paper or fiber, and to provide a constant pitch which is predetermined in accordance with the desired number of R. P. M. to be imparted to the package during subsequent high twisting operations. After the pitch has been determined, the traverse ratio can in turn be calculated, depending upon the length of the package. Furthermore, it has been discovered that by using a lower pitch than has heretofore been used, various types of yarns can be unwound at considerably higher R. P. M. than was heretofore possible, e. g., substantially above 10,000 R. P. M., and even as high as 20,000 R. P. M.

In describing the present invention and the prior art, reference will be made to the length and pitch of a course of yarn wound on a bobbin and to facilitate consideration of these dimensional data there is shown in the single figure of drawing a schematic view of a bobbin with thread cross wound thereon. The dimension S represents the pitch of the cross wind and the dimension L represents the axial length of the wound body from a: to y as distinct from the overall length of the core on which the winding takes place.

Before describing this invention in detail, a description of the operations prerequisite to the high twisting step will be given and the problems heretofore involved therein.

Yarns that are used for stockings and the like must be twisted from 500 to 1200 turns per meter, and in the so-called crepe yarns, range from 1500 turns or more per meter.

It is necessary when manufacturing highly twisted yarns, to subject normally twisted yarns to an additional twisting operation. The aftertwisting operation may take place by positioning a cross wound bobbin containing normally twisted yarn on a vertical upright throwing assassa spindle. This spindle is rotated while the yarn is drawn off overhead and led to a take-up bobbin upon which it is wound tangentially. It is obvious that both the number of revolutions of the vertical spindle and the peripheral speed of the take-up bobbin determine the number of additional turns imparted to the yarn. For example, assuming that the normally twisted yarn contains 100 turns per meter and it is required to raise it to 700 turns per meter, an increase of 600 turns per meter, then the spindle may be rotated 3000 R. P. M. and the take-up roller is rotated to give a peripheral speed of meters per minute. By so doing, the yarn is twisted 3000+5 which equals 600 turns per meter. Of course, the same result can be obtained by rotating both the supply bobbin and the take-up bobbin at higher or lower speeds, but at the same relative speeds.

From the above, it is apparent that when it is necessary to increase the number of turns per meter, the cross' wound supply bobbin must be rotated faster, or the speed of the take-up bobbin must be decreased. However, the speed of the take-up bobbin determines the production capacity for the after-twisting operation, and since the rotation of the supply bobbin prior to the present invention could not exceed practical limits, the take-up bobbin had to be rotated at a relatively slow speed, which reduced the production capacity.

As heretofore stated the previously twisted cross wound supply packages offer a number of advantages over the old type packages wound on flanged bobbins. These cross wound bobbins are wound with a traversing device which eifects an uninterrupted crossing of the yarn coils from one end of the bobbin to the other and are selfsupporting, thereby eliminating the necessity of flanges at each end. The core of such a bobbin is much smaller in diameter and therefore can accommodate a considerably larger package having the same over-all diameter as that of the flanged bobbin.

However, when using the cross wound bobbins as the throwing packages, unsatisfactory results have been realized when the packages exceed 100 gms. in yarn weight, and when the packages were unwound at high R. P. M.s.

When it was attempted to increase either the weight of the yarn per bobbin or the speed of unwinding by means of throwing spindles constructed as the extension of the rotor shaft of an electric motor, or both, the results were completely unsatisfactory. The increase in weight of yarn and number of revolutions resulted in the formation of so-called Satums rings, formed by the untimely loosening of the thread coils from the bobbin, which caused entanglement and finally breakage of the thread during the twisting operation.

During the experiments however, for the then unexplainable reason, some of the heavier cross wound bobbins were successfully after-twisted at higher R. P. M. than used in practice, so that it was concluded that there were still unknown factors having sometimes a poor effect and sometimes a good efiect on the after-twisting. It was finally discovered that the nature of the buildup of the cross wound bobbin had a definite relation to the number of R. P. M. which could be utilized to attain a practical subsequent twistproducing the cross wound bobbins wer R. P. M. of the bobbin number of full traverse strokes per minute A back and forth movement of the traverse device which covers a path 2L constitutes a full traverse stroke. In normal practice the traverse ratio is usually from 4:1 to 5:1 for bobbins of about 10 cm. in length.

In producing cross wound bobbins according to this method, the desired pitch of the yarn on the bobbin is used to determine the traverse ratio for any given length. The pitch is not to be confused with the angle or inclination or the tangent thereof, but it is the distance (in cm.) of two corresponding points on two successive paths of the yarn, which distance is indicated by the letter S. If S is constant, K varies in proportion to L, and the following equation applies:

It can be readily seen from this equation that as the length of the stroke of the traverse increases, the traverse ratio will increase when the pitch is constant. Thus, a constant pitch can be pro-- duced regardless of the length of the stroke. When producing cross wound bobbins according to this method, the R. P. M. of the bobbin being constant, as the diameter increases, the peripheral speed will increase, and consequently the yarn take-up increases per unit or time. This affects the helix angle of the winding but does not afiect the pitch as defined above.

In the second method of producing cross wound bobbins the take-up bobbin i driven by a friction roller which rotates at a constant speed, thereby imparting to the take-up bobbin a constant peripheral speed. Here again a traversing device is used which causes the yarn to pass through the length L of the package.

Although the second method provides for a constant take-up of the yarn per unit of time so that the supply is regular, after studying the two methods of winding, it was determined that the second method could not be used. Since the number of revolutions per minute to be used in the subsequent high twisting operation was dependent on the pitch of the cross wound bobbins, it is obvious that the second method wherein the R. P. M. was constantly changing, caused the traverse ratio and therefore the pitch to constantly change. Accordingly, the first method had to be adopted, namely. that in which the R. P. M. remained constant, so that the same traverse ratio was maintained throughout all layers of the cross wound package, and by Formula 1 the pitch was kept constant.

As a result of many experiments it was determined that there was a minimum traverse ratio, 1. e., maximum pitch at which the subsequent high twisting operation became commercially practical, and that said ratio or pitch can be determined from the desired R. P. M. of the throwing bobbin.

The minimum value of the traverse ratio K may be represented by K'=aTL in which T is the number of R. P. M- to be imparted to the throwing bobbin, L is the length of the stroke or package, and a is a factor dependent upon the type of yarn being wound. K indicates a lower limit value, but in practice it is preferable to increase this value to K", which is determined by K"=aTL+bL in which b is a safety factor constant dependent upon the type of yarn used.

Since the results of the present invention are largely achieved by predetermining the ratio of the pitch of the windings to the number of R. P. M. to be imparted to the throwing bobbin, regardless of the stroke length L, it is desirable to set up an operating formula in which L is not a factor. This may be derived as follows:

Since 2L =arL+bL Now dividing both sides by 2L:

1 (1T b s am and solving for S:

2 (2) -zfit The constants a and b for viscose yarn are and respectively. Thus with the knowledge of the desired R. P. M. of the throwing bobbin, the pitch of the wind is determined and from this the traverse ratio is computed by Formula 1. Note, however, that the pitch itself is wholly independend of L even though L must be a factor in the computation of K.

For example, suppose it is desired to turn the throwing bobbin at 10,000 R. P. M. Then from Formula 2:

With this pitch and using a 10 cm. bobbin, the traverse ratio from Formula 1 is:

If the bobbin were 20 cm. long instead of 10 then:

, 5 If it is desired to turn the throwing bobbin at 20,000 R. P. M., then:

With this pitch and using a 10 cm. bobbin, the traverse ratio is:

If the bobbin were 20 cm. long instead of 10, then:

40 K E 0r22 It is apparent from these equations why it has not been possible in past practice using the normal cross wound bobbins to apply very high R. P. M. during the high twisting operation. This is apparent since in the prior art, traverse ratios of 4:1 to 5:1 are contemplated without regard to the length of the package. Yet it has been demonstrated that a ratio of 5:1, while it might be suitable for a very short package, would not be at all suitable for a longer package in that th critical value of S would not be achieved.

According to this invention, it is now possible to twist off cross wound bobbins without incurring any trouble in ranges of 10,000 to 20,000 R. P. M. In order to revolve the throwing spindle at such high speeds, it has been found preferable to use electrically driven spindles. These twisting spindles are formed as the extended rotor shafts of an electric motor, so that transmissions are eliminated. This results in a considerable increase in output and yet at a great saving of power consumption. Even in the best constructed mechanically driven twisting spindles, difficulties are incurred when the R. P. M. exceed 10,000. This is especially true with larger bobbins having a yarn weight greater than one pound, in which the power consumption per spindle rapidly increases to a point where the opera tion becomes impracticable.

The invention including the experiments, the formulae, and the constants, determined in connection therewith, all relate to normal continuous filament viscose rayon having deniers of from 40 to 150, and treated with the standard type finishing agents and twisted normally from about 75 to turns per meter under a uniform tension.

In the case of other yarns such as acetate silk or natural silk, or Nylon, or protein yarn, and similar yarns, or with yarns finished in a special manner, the values of (la) and (b) necessary for good twisting conditions in the above equations may differ from the values of normal viscose yarn. However, by simple experiments to determine the relation of the pitch to the number .of R. P. M. that the high twisting operation begins to be possible, the value of (a) may immediately be determined. Then by subsequent investigation the safety factor constant (b) may be determined, at which the after-twisting will always proceed satisfactorily. If the surface of the yarn is rougher than normal, or if the elasticity is less, or if the cross wound bobbin is wound under a 7 special tension, the sloughing oil of the outside layers will occur less, and therefore. a higher pitch in general may be suiiicient. In any case, the general formulae given above will oifer a sufficient basis to readily calculate the new constants.

What is claimed is:

1. A process of producing cross wound packages of normal viscose yarn suitable for high speed rotation on a throwing bobbin which comprises winding a previously twisted yam at a pitch that is constant throughout the body of the package and is determined by the formula 2 aT+b where 8 is equal to the pitch, '1 is equal to the desired R. P. M. of the throwing bobbin, and (a) and (b) are constants.

2. A process of producing cross wound packages of normal viscose yarn suitable for high speed rotation on a throwing bobbin which comprises winding a previously twisted yarn at a pitch that is constant throughout the body of the package and is determined by the formula 2 117 +0 where S is equal to the pitch, T is equal to the desired R. P. M. of the throwing bobbin, and (a) and (b) are constants having the value prises winding a previously twisted yam at a pitch that is constant throughout the body of the 4 package and is determined by the formula 8 where 8 ranges from 3% cm. to 1%; cm., allowing throwing bobbin speeds of between 10,000 and 20,000 R. P. M. respectively, and (a) and (b) are constants having a value of and 20000 10 respectively.

4. A process of producing cross wound packages of normal viscose yarn suitable for high speed rotation on a throwing bobbin which comprises winding a previously twisted yarn at a constant pitch throughout the body of the package that bears the following relationship to the R. P. M. to be imparted to the throwing bobbin:

PETRUS ANDRES BEEFTINK.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,110,926 Williams Mar. 15, 1938 2,119,963 Ramsdell June 7, 1938 2,259,364 Bartholomew Oct. 14, 1941 

